The present invention relates to a method of monitoring the operation of a cellular radio system in a system comprising at least a base station and a repeater tuned to repeat signals sent by the base station on traffic channels, and in which system the base station sends over the radio path a traffic channel list including traffic channels at its disposal. The invention further relates to a repeater in a cellular radio system, the repeater comprising: amplifier units for receiving, amplifying and forwarding signals sent by a first base station on traffic channels, and a transceiver unit for setting up a signalling connection to other system parts to transfer control signals between the repeater and other network parts.
A problem associated with known cellular radio systems is management of the repeaters used in the system. In known systems, repeaters inform their configurations to other network parts only when required by the management system. Consequently, in reconfiguration of system traffic channels, for example, situations may arise when a repeater is tuned by mistake e.g. to the wrong traffic channels or its tuning is completely neglected, leaving it on old traffic channels. In this case, because of the wrong traffic channels, the repeater is no longer able to repeat traffic channels of the base station it should repeat. Since known repeaters inform their configuration only when required, a repeater may remain for a long time on the wrong traffic channels before the management system detects the mistake e.g. because of impaired audibility within a given network area.
Aspects of the present invention are to solve the above problem and to provide a solution for enhancing and facilitating the monitoring of the operation of a cellular radio system. These aspects are achieved by a method in which a repeater is adapted to receive a traffic channel list sent by the base station, the traffic channels included in the traffic channel list are compared with the traffic channels used by the repeater, and an alarm is given if the traffic channels used by the repeater differ from the traffic channels included in the traffic channel list.
The invention also relates to a repeater in a cellular radio system for applying the method of the invention. The repeater includes a transceiver unit that is adapted to receive a traffic channel list sent by the first base station over the radio path and that includes all traffic channels at its disposal. The repeater also includes comparison means for comparing the traffic channels included in the traffic channel list with the channels used by the amplifier units, and the transceiver unit includes means for sending a predetermined message to a management system of the system when the comparison means indicate that the channels used by the amplifier units of the repeater differ from the traffic channels included in the traffic channel list.
In this context the concept traffic channel list refers to a list sent by a base station over the radio path and which includes traffic channels allocated to the use of the base station. For example in the GSM system (Global System for Mobile communications), base stations send in accordance with GSM specification part 04.08 on a BCCH channel (Broadcast Control CHannel) a Base Allocation list indicating said information.
The invention is based on an idea to significantly enhance and facilitate the management of a cellular radio system, once system repeaters are adapted to monitor the traffic channels used by corresponding base stations. In accordance with the invention, each repeater is adapted to receive a traffic channel list sent by the corresponding base station over the radio path. In this case the repeater immediately detects possible malfunction, i.e. a situation where the channels included in the traffic channel list differ from the channels used (repeated) by its amplifier units. In this situation the repeater immediately sends information on the detected malfunction to the management systems of the system. The repeater may simultaneously monitor the operation of the corresponding base station. That is, in case of malfunction of a base station, a repeater detects it because it is no longer able to receive signals sent by the base station. Also in this situation the repeater reports this to the management system of the system. Thus the most significant advantages of the method and repeater of the invention are that the repeaters are able to independently detect a situation in which they are tuned to repeat the wrong channels, that the repeaters are able to monitor the operation of the corresponding base station, and that the repeaters are able to send on their own initiative information to the management system about a malfunction they have detected, whereby the management system (and operator) detect a malfunction more rapidly and easily than previously.
In one specific embodiment of the method of the invention, the repeater is adapted to measure signal strengths of signals transmitted by base stations audible to it, the measured signal strengths are compared with each other, and an alarm is given if the comparison indicates that the strongest signals received by the repeater have been sent by some other base station than said first base station. This embodiment of the invention enables monitoring of the operation of the base stations in the system. In addition to being able to monitor the operation of the corresponding base station (i.e. the base station whose signals it repeats), the repeater may simultaneously also monitor the operation of other base stations in the system. This may take place by the repeater maintaining in its memory a list of the strongest base stations audible to it, and at given intervals make control measurements in order to find out if the audibility of the base stations has changed. If in this case a base station is significantly less audible than previously (or not at all), the repeater may send information about this to the management system.